This invention generally relates to the exchange of dilatation catheters by means of an extension wire in procedures such as percutaneous transluminal coronary angioplasty (PTCA).
In PTCA procedures with over-the-wire balloon dilatation catheters, a guiding catheter having a preshaped distal tip is percutaneously introduced into the cardiovascular system of a patient and advanced therein until the preshaped distal tip thereof is disposed within the aorta adjacent the ostium of the desired coronary artery. The guiding catheter is twisted or torqued from its proximal end, which extends outside of the patient, to turn the distal tip of the guiding catheter so that it can be guided into the coronary ostium and seated therein. A dilatation catheter having an inflatable member on the distal end thereof and a guidewire slidably disposed within an inner lumen of the dilatation catheter are introduced into and advanced through the proximal end of the guiding catheter to the distal tip of the guiding catheter seated within the coronary ostium. The distal tip of the guidewire is usually manually shaped (e.g. curved) by the physician or one of the attendants before it is introduced into the guiding catheter along with the dilatation catheter.
The shaped distal tip of the guidewire is first advanced out the distal tip of the guiding catheter into the patient's coronary artery. Torque is applied to the proximal end of the guidewire, which extends out of the proximal end of the guiding catheter, as the guidewire is advanced within the coronary anatomy, to guide the curved or otherwise shaped distal end of the guidewire into the desired branch artery targeted for dilatation. The advancement of the guidewire within the target artery continues until it crosses the lesion to be dilated.
The balloon dilatation catheter is then advanced out of the distal tip of the guiding catheter, over the previously advanced guidewire, until the balloon on the distal extremity of the dilatation catheter is properly positioned across the lesion to be dilated. Once properly positioned across the lesion, the flexible, relatively inelastic dilatation balloon on the catheter is inflated to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations of the balloon may be required to complete the dilation. After the last dilation, the balloon is deflated so that the dilatation catheter can be removed from the dilated stenosis and so that blood flow can resume through the dilated artery.
Further details of guiding catheters, dilatation catheters, guidewires, and the like for angioplasty procedures can be found in U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,438,622 (Samson et al.); U.S. Pat. No. 4,554,929 (Samson et al.); U.S. Pat. No. 4,582,185 (Samson); U.S. Pat. No. 4,616,652 (Simpson); U.S. Pat. No. 4,638,805 (Powell); U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,898,577 (Badger et al.); U.S. Pat. No. 4,748,982 (Horzewski et al.); U.S. Pat. No. 4,821,722 (Miller et al.); U.S. Pat. No. 4,827,943 (Taylor et al.); U.S. Pat. No. 4,898,577 (Badger et al.); U.S. Pat. No. 4,966,163 (Kraus et al.); and U.S. Pat. No. 4,998,923 (Samson et al.) which are incorporated herein in their entirety by reference thereto.
It is not uncommon during an angioplasty procedure for the dilatation catheter to be exchanged. While there are a variety of reasons for such catheter exchanges, it is usually done to provide a dilatation catheter with a more appropriately sized balloon. To effect the catheter exchange, typically an elongated extension wire is secured to the proximal end of the guidewire which extends out of the patient. The length of the guidewire and the extension wire which extends out of the patient must be longer than the length of the dilatation catheter to facilitate the catheter exchange without the loss of guidewire position within the patient's artery. The dilatation catheter is withdrawn from the patient over the guidewire and the extension wire until the distal end of the dilatation catheter exits the proximal end of the guiding catheter which extends out of the patient. The exposed portion of the guidewire which extends out of the guiding catheter but which is distal to the distal end of the withdrawn dilatation catheter may then be held manually so as to retain the position of the guidewire within the patient's vasculature while the dilatation catheter is completely removed from the guidewire and the extension wire.
A replacement dilatation catheter or other type catheter is then mounted onto the proximal or free end or the extension wire and advanced over the extension wire and over the guidewire connected thereto to a desired location within the patient's vasculature where additional intravascular procedures may be performed. The extension wire is usually removed, if possible, before proceeding with the additional intravascular procedure.
The aforementioned Taylor et al. patent discloses a connection of the proximal end of a guidewire to the distal end of an extension wire wherein the proximal end of the guidewire has an undulating member which frictionally engages a tubular member on the distal end of the extension wire. While this connection has been well received by the medical profession, occasionally the connection would fail and disrupt the angioplasty procedure. The Kraus et al. patent describes a system for exchanging a dilatation catheter over an extension wire wherein the proximal end of the guidewire, which extends out of the patient, is secured by a threaded connection to the distal end of an extension wire. While this system has also been well received by the medical profession, its use has been limited to angioplasty procedures in peripheral arteries due to its relatively large size. Threaded connections dimensioned for coronary angioplasty use could not be readily made by conventional methods because there is presently no convenient way of making female threads within a tubular member with an internal diameter less than about 0.02 inch, which is of the size needed for coronary angioplasty.
What has been needed and heretofore unavailable is a threaded connection system which is small enough to be used to connect an extension wire to a guidewire dimensioned for coronary angioplasty and which soundly connects the two components. The present invention satisfies this and other needs.